1. Field of the Invention
The invention relates to a method for shaping the surface of extruded profiles made of thermoplastic materials with a device, which is profiled to the shaping of the surface such that it is complimentary to the required shaping dimensions and presses these into the continuous profile.
2. Description of the Related Art
A device of this type is described in U.S. Pat. No. 2,075,735 which is designed according to a shaping apparatus. With this imprinting apparatus, the imprinting elements are arranged continuously on a conveying belt in a creeper chain manner whereby these elements are arranged on both sides of the just produced imprinting profile and impinge on the latter. Hereby, the imprinting surface is still warmed by the original shaping method and can be heated if necessary. The shaping dimensions are formed complimentary in the imprinting apparatus and are pressed into the continuous profile.
This device is very costly in its construction and therefore very expensive and prone to failure. A further disadvantage of this device is that it can only be used for each respective continuous profile. If a profile needs to change, removal is timexe2x80x94and cost-consuming, and a new device for the respective profile has to be mounted.
A further device of this type is described in EP 0 092 745.
This relates to a device for imprinting the surface of thermoplastic materials immediately after its shaping process in a warm-plastic state. The used imprinting tool is profiled complimentary at its peripheral surface to the desired imprinting dimensions and presses these into the passing profile material.
Thereby, a negative pressure arrangement in the area of the imprinting tool, which is formed as a roller, sucks the profile material against the unwinding peripheral roller surface. The imprinting roller proceeds with part of its circumference through an opening of the low-pressure chamber and is arranged at the front of a calibrating nozzle.
The roller runs in the manner of a rolling seal over the imprinting and still workable surface of the profile material, whereby, by means of the sucking effect which pulls the profile material against the imprinting roller, its surface is provided with the required profiling corresponding to the outer profile of the printing roller in a fine, clear manner without leaving undesired shaping traces. The obtained sucking effect is sufficient to pull the surface of the profiling material against the imprinting roller so that a clean imprint is achieved but only a very small dynamic effect is derived that the dimensional accuracy of the profile material is not permanently impaired. A further advantage consists in that the imprinting process occurs after the extrusion when the profile material can still be shaped and undesired deformations can be prevented.
A disadvantage of this device, which is generally only used for hollow chamber profiles, is the cost of construction. Moreover, the shaping takes place in the warm-plastic area. After the shaping, the profile material cools down and due to the relaxation, the contours of the imprints fade with time. A further disadvantage is that the method for imprinting the surface of the profile material takes place by applying a vacuum. For this process quite extensive devices are necessary whereby the control and timing of the imprinting method become very difficult. The imprinting rollers used have the same width as the continuous profiles and can lead to damage and deformation in the marginal areas of the continuous profiles.
A further disadvantage of this method is that the device used for this imprinting process partially penetrates the surface of the continuous profile materials causing damage to these materials. Further, an indentation results from the shaping dimensions within the profile material and thereby initiates potential ruptures.
The object of the present invention is to improve the known state of the art technology in such a manner that a method and a device are provided which simply, economically and with high accuracy indicate a material-saving manufacturing of profiles with a full retention of the required stability at the same time.
This is achieved with the embodiment according to the characterizing features of the present invention. The shaping profile is cooled down in a first processing step and supplied to the shaping device in a dimensionally stable state. In the second processing step, the shaping device presses the desired shaping dimensions into the continuous profile so that the surrounding edges of the impressions are reduced in their wall strength and thereby work-hardened. In a third process step, the imprinted profiles are cut down and deposited into defined units.
In a further advantageous embodiment of the method according to the invention, the shaping C- or U-profile is cooled down in a first processing step and supplied to the shaping device in a dimensionally stable state. In a second processing step, the side walls of the C- and U-shaped profiles are fastened and in the third processing step, the desired shaping dimensions are pressed by means of the shaping device into the continuous C- or U-shaped profile. The surrounding edges of the impressions are thereby reduced in their wall strength and work-hardened. In a fourth processing step, the side walls of the C- or U-shaped profile are retained in their fastened state and in a fifth processing step returned to their initial state. In a sixth processing step, the imprinted C- or U-shaped profiles are cut down and deposited into defined units.
The advantage of this method is that profiles are manufactured in a simple and cost-effective manner for which a lower material expenditure is possible with the same mechanical characteristics. The manufacturing of these profiles is more effective since the cooling periods and therefore the entire manufacturing time can be reduced by the reduced wall strengths.
A further advantage of this method is that it can be applied nearly independently from the used profiling dimensions whereby only the desired shaping dimensions define the required shaping device.
A further important advantage of the shaping device is that the profiles are cooled down and can be shaped in a dimensionally stable state in such a manner that the height of the impressions corresponds at least to half the wall strength of the continuous profile.
In an advantageous embodiment, the shaping device is an opposed rotating imprinting tool comprising at least one stamping roller and at least one matrix ring.
The gap, i.e., the distance between the highest point of the stamping roller and the highest point of the matrix ring, corresponds at least to the wall strength of the continuous profile.
Advantageously, the distance between the highest and the lowest point of the stamping roller corresponds in the area of the impression at least to half the wall strength of the continuous profile. Thereby, the surrounding edges of the impressions are reduced in their wall strength, work-hardened and lead to a particular stabilisation of the continuous profile. The distance between the highest and the lowest point of the matrix ring also corresponds at least to half the wall strength of the continuous profile so that this reduction in wall strength and the resulting consolidation of the profile material is obtained.
In a further advantageous embodiment of the device according to the invention, one or several stamping rollers and one or several corresponding matrix rings are integrated in the arrangement.
These can be arranged without a drive and freely rotatable so that the speed of the opposed imprinting tools is defined by the discharge speed in the extrusion section.
In a further advantageous embodiments the stamping rollers and matrix rings have common drive units, and their speeds are approximately equal to the discharge speed of the continuous profile in the extrusion section.
In a further embodiment, the shaping device comprises at least one stamping tool of a defined length with at least one complimentary abutment. This embodiment can be formed in such a manner that the stamping tool with the complimentary abutment in axial direction, that is in the direction of extrusion, is arranged movably and carries out intermittent movements. Thereby, the shaping process can be carried out in a cost-effective manner in the extrusion section as the shaping tool moves at the same rate as the continuous profile.
In a further embodiment according to the invention, the shaping tools is designed in such a manner that the stamping tool and the complimentary abutment can carry out a movement perpendicular to the direction of extrusion.
This is, for example, of advantage at relatively low extrusion speeds whereby the shaping profile piece is clamped and the desired shaping dimensions are applied while the continuous profile is stocked up in the extrusion section.
Hereby, the costs for the shaping tool can be kept at a low level which has a positive effect on the price of the finished product.
With this embodiment too, the distance between the highest point of the stamping tool and the highest point of the complementary abutment is carried out at least with the wall strength of the continuous profile. A further advantage in this embodiment is that the distance between the highest point and the lowest point of the stamping tool in the area of the impressions is designed at least with half the wall strength of the continuous profile. The distance between the highest and the lowest point of the complimentary abutment is advantageously designed in the area of the impression at least with half the wall strength of the continuous profile.
Thereby it is achieved that the hardening in the surrounding edge region of the impressions is obtained and a profile is produced which has a lower initial wall strength and the same mechanical stability as commonly manufactured profiles according to the state of the art technology.
A number of embodiments of shaped profiles are explained in detail by means of schematic drawings.